IR: Stop using DIDescriptor::is*() and auto-casting

`DIDescriptor`'s subclasses allow construction from incompatible
pointers, and `DIDescriptor` defines a series of `isa<>`-like functions
(e.g., `isCompileUnit()` instead of `isa<MDCompileUnit>()`) that clients
tend to use like this:

    if (DICompileUnit(N).isCompileUnit())
      foo(DICompileUnit(N));

These construction patterns work together to make `DIDescriptor` behave
differently from normal pointers.

Instead, use built-in `isa<>`, `dyn_cast<>`, etc., and only build
`DIDescriptor`s from pointers that are valid for their type.

I've split this into a few commits for different parts of LLVM and clang
(to decrease the patch size and increase the chance of review).
Generally the changes I made were NFC, but in a few places I made things
stricter if it made sense from the surrounded code.

Eventually a follow-up commit will remove the API for the "old" way.

llvm-svn: 234255

1 files changed, 3 insertions, 9 deletions

diff --git a/llvm/lib/IR/DebugLoc.cpp b/llvm/lib/IR/DebugLoc.cpp
index 95f6d67c542..df4802d9549 100644
--- a/llvm/lib/IR/DebugLoc.cpp
+++ b/llvm/lib/IR/DebugLoc.cpp
@@ -50,8 +50,7 @@ MDNode *DebugLoc::getInlinedAtScope() const {
 DebugLoc DebugLoc::getFnDebugLoc() const {
   // FIXME: Add a method on \a MDLocation that does this work.
   const MDNode *Scope = getInlinedAtScope();
-  DISubprogram SP = getDISubprogram(Scope);
-  if (SP.isSubprogram())
+  if (DISubprogram SP = getDISubprogram(Scope))
     return DebugLoc::get(SP.getScopeLineNumber(), 0, SP);
 
   return DebugLoc();
@@ -87,13 +86,8 @@ void DebugLoc::print(raw_ostream &OS) const {
     return;
 
   // Print source line info.
-  DIScope Scope(getScope());
-  assert((!Scope || Scope.isScope()) &&
-         "Scope of a DebugLoc should be null or a DIScope.");
-  if (Scope)
-    OS << Scope.getFilename();
-  else
-    OS << "<unknown>";
+  DIScope Scope = cast<MDScope>(getScope());
+  OS << Scope.getFilename();
   OS << ':' << getLine();
   if (getCol() != 0)
     OS << ':' << getCol();